Your Future iPhone May Be Stuffed With Wax

A team of academics is using wax -- yes, wax -- to explore a whole new breed of smartphone chips. Original video: Steve Crang/Mike Hensel

Inside a research lab at the University of Michigan, there’s an Intel chip covered in wax.

It’s a Core i7 microprocessor — the same chip that runs many of today’s desktop and laptop PCs — and the wax is stuffed into a metal mesh surrounding this tiny sliver of silicon. When someone cranks the chip well beyond its recommended speeds, the wax absorbs the extra heat coming off the silicon, and at 54 degrees Celsius, it starts to melt.

No, it’s not a party trick. It’s a look into the future of the tiny processors that run on our smartphones and tablets. This waxed chip is a prototype, a test system built to solve an engineering problem threatening to shackle the performance of our computer chips.

The problem facing today’s chips is this: Stuffed with billions of transistors, they’re beginning to use too much power in too small a space. If mobile phones actually used all of their transistors at the same time, they’d overheat, and researchers say this issue will only get worse as transistors get smaller.

‘What makes computing so great is they are general purpose devices that you can program to do anything’

— Milo Martin

This is why a smartphone chip often power down parts of itself when they’re not being used (the industry term for this is dark silicon). Apple’s A5 processor, used in iPads and iPhones, for example, has a general purpose processing unit — a CPU — but about half of the chip is devoted to specialized processors that are used only part of the time.

The trouble is that this model has its limits. “There are only so many things that you can specialize,” says Milo Martin, an associate professor with the University of Pennsylvania.1 “What makes computing so great is they are general purpose devices that you can program to do anything.

Martin and his fellow researchers at the University of Michigan and the University of Pennsylvania have a different plan for all of those power-hungry transistors. “We said, ‘Maybe it’s OK to use them all, just don’t use them very long,'” he explains.

The group believes that microprocessors can reach a new level of performance if we built them to sprint rather than jog — if we juice them to seemingly insane levels and then give them time to rest, before juicing them back up again. The wax — or paraffin — is there to keep them from overheating during these intermittent sprints.

They call it “computational sprinting,” and they’ve been tinkering with it since 2010. This year, they set up an Intel Core i7 test processor with a custom cooling system that could run comfortably at a maximum of 10 watts of power. In their tests, though, they would periodically boost the chip to 50 watts. That’s enough power to overheat the chip in a matter of seconds, but it speeds up the chip’s clock speed and it uses more transistors.

They think they could eventually boost that chip up to 100 watts for short periods of time. So, it would briefly do an amazing amount of computing, but it would get mighty hot too. That’s where the wax comes in. It’s great for absorbing a lot of heat really quickly — until it melts.

They say that by turning chips into sprinters, they can do more than just handle the short-term bursts of computation you need to pop up new windows on your smartphone. They think that this Tortoise-and-the-Hare sprinting style can actually save energy.

Martin even envisions sprinting servers and supercomputers too. “There are actually some situations where it makes more sense to operate in sprint and rest,” he says.

An experimental chip with divots etched onto its surface. The divots would then be filled with a material like wax to absorb heat from a sprinting CPU. Photo: Lei Shao

Does that mean we’ll all see waxy heat-absorbing materials slid into our madly sprinting mobile phones? Not anytime soon. It may take five to 10 years. These materials cost too much at the moment. But this sprinting model is very much in line with the way that people use their mobile phones, say Intel engineers Per Hammarlund and Steve Gunther.

“We see this as very important, and it’s an area where we have been putting in a lot of of effort, and we’re continuing to put a lot of effort into it,” says Hammarlund. When you consider how most people use mobile phones, sprinting makes a lot of sense. “You appreciate having really snappy responsive system behavior for very short bursts of time. And other than that, you really want the system to consume no power.”

In fact, Intel chips have been doing something very similar to sprinting since around 2008. Intel’s technology, called Turbo Boost, can double consumption when the chip is in sprint mode. That’s a lot less than the systems being tested by the Michigan and Penn researchers. But there’s a lot more to do. “Intel’s Turbo Boost isn’t really sprinting as we’ve explored it,” he says. “Perhaps it is jogging.”

Martin thinks that it might make sense to design chips from the ground up to be overused, almost like hot-rod engines. But Intel stressed that we must balance these ideas with what happens in the real world. The company draws on a whole arsenal of tricks to manage system performance and draw out battery life.

“There are lots of different things to be concerned about down this path,” says Intel’s Gunther. “If I solve my thermal problem over a short time period with a piece of wax, that’s great. But if I can’t get the current out of the battery … it doesn’t help. You need balanced solutions.”

Sure you do. But eventually, we’ll also need something new.

1Correction 12:50pm EST 08/22/13: This story originally misidentified Milo Martin’s university affiliation. He is an associate professor with the University of Pennsylvania